Sensor Module; Photo Multiplier Tube (Pmt); Figure 6-17. Basic Pmt Design - Teledyne T200 User Manual

SENSOR MODULE

The sensor assembly (Figure 5-20) consists of several subassemblies, each with different
tasks:
The Photo Multiplier Tube (PMT) detects the intensity of the light from the
•
chemiluminescence reaction between NO and O
current signal that varies in relationship with the amount of light in the reaction cell.
• The PMT Preamplifier PCA converts the current output by the PMT into a voltage and
amplifies it to a signal strong enough to be usable by the motherboard's A à D
converter. It also supplies the drive voltage and gain adjustment for the PMT's High
Voltage Power Supply (HVPS)
• The Thermo-Electric Cooler (TEC) controls the temperature of the PMT to ensure the
accuracy and stability of the measurements.

PHOTO MULTIPLIER TUBE (PMT)

The analyzers use a photo multiplier tube (Figure 5-20) to detect the amount of
chemiluminescence created in the Reaction Cell.
A typical PMT is a vacuum tube containing a variety of specially designed electrodes.
Photons from the reaction are filtered by an optical high-pass filter, enter the PMT and
strike a negatively charged photo cathode causing it to emit electrons. A high voltage
potential across these focusing electrodes directs the electrons toward an array of high
voltage dynodes.
The dynodes in this electron multiplier array are designed so that each stage multiplies the
number of emitted electrons by emitting multiple, new electrons. The greatly increased
numbers of electrons emitted from one end of the electron multiplier are collected by a
positively charged anode at the other end, which creates a useable current signal. This
current signal is amplified by the preamplifier board and then reported to the motherboard.
083730200A DCN7962

Figure 6-17. Basic PMT Design

Teledyne API T200 NO/NO
in the reaction cell. It outputs a
3
/NO Analyzer with NumaView™ Software
2 x
207